Right from the first triple model, the 1968 Mach III H1 500 cc, it was a sales success that gained a reputation for almost unmatched acceleration as well as an air of danger for inexperienced riders trying to cope with the bike's increased power to weight ratio over any previously available stock motorcycles.

[2] While Kawasaki had an inline-four, four-stroke engine in development, it was not going be ready in time to upstage the 1969 Honda CB750, so instead they moved up the release of their conventional piston-port two-stroke triple, with one 2009 writer describing it as "...something that would make a real splash".

[3] The first version of this electronic ignition was overly complex and proved unreliable, so Kawasaki gave up on it briefly, using traditional breaker points, one set for each cylinder, in 1972.

[2] For the 1973 H1D, a redesigned CDI was used, which was more reliable with a hotter spark at lower engine speeds, which in turn made it possible to re-jet the three Mikuni carburetors for a wider power band.

[1] The H1 had a high power-to-weight ratio for the time, 45 kW (60 hp) and a dry weight of 384 pounds (174 kg), comparable to a top racing motorcycle, but had generally poor handling and weak drum brakes front and rear.

[5] When the H1 was first announced, Motorcycle Mechanics criticised Kawasaki for their "own ambitious claim" that it was "the fastest and best accelerating road machine ever produced, being capable of 124 mph and 12.4 sec.

[10] According to a 2020s motorcycle business, Kawasaki had an early production model H1 delivered to Lyon's Drag Strip, an AHRA sanctioned drag strip in Southern California were they uncrated it, put fuel in it and with Tony Nicosia as the rider it went 12:96 seconds making the Mach III officially the first production motorcycle to cover 1/4 mile from a standing start in less than 13 seconds.

[9] While Kawasaki was working to "make the H1 acceptable in civilized society", they also released the delayed inline-four four-stroke, the Z1, in 1972, which had adequate brakes and handling, comfortable seating, and did not guzzle fuel.

"[4] While older Baby boomers collected classic brands of the 1950s and 1960s like BSA, Norton and Triumph, a younger generation of motorcycle collectors was nostalgic for H1 Mach IIIs along with other bikes of the era, Honda CBs and CLs, Yamaha RD350s and Suzuki Hustlers.

With larger displacement as well as less aggressive porting and ignition timing,[13] the H2 750 had a wider power band than the 500 H1, though Brown said it was still "barely more practical" than the smaller predecessor, because Kawasaki had "done little" to address chassis problems, and so the bike was still prone to speed wobble.

[7] The 14 bhp (10 kW) gain over the 500 H1 put the H2's output well ahead of its close rivals, the air-cooled four-stroke Honda CB750 and the liquid-cooled two-stroke Suzuki GT750.

[7] The H2 had a front disc brake, an all-new capacitor discharge ignition system which performed better than cap and rotor type, was virtually maintenance free, and was unique to the H2.

[20] The H2 was part of the rise of the Japanese superbikes, contributing to the decline of Harley Davidson, and nearly extinguished the British motorcycle industry in the US for a long period.

This usage stopped in February 1981, however, when learners were restricted to 125cc/12 bhp, and virtually overnight the sales of new 250cc machines ceased, not really taking off again until the Big Four started producing high performance 250s in the mid to late 80s in the form of the RG250 (later RGV), TZR, NSR and Kawasaki's class leading (but fragile) KR1 and KR1s.